Thermal device having rotatable heater and flexing actuator



- Oct. 5, 1965 J. L. SLONNEGER 3,210,502

THERMAL DEVICE HAVING ROTATABLE HEATER AND FLEXING ACTUATOR Filed April26, 1963 [/7 1 6 2723'07": 39 53 Jo/mLS/anneger;

United States Patent 3,210,502 THERMAL DEVICE HAVING ROTATA-BLE HEATERAND FLEXING ACTUATOR John L. Slonneger, Morrison, 11]., assignor toGeneral Electric Company, a corporation of New York Filed Apr. 26, 1963,Ser. No. 276,053 11 Claims. (Cl. 200122) My invention relates tothermally responsive devices, such as bimetallic switching devices, andmore particularly to switching devices which employ an elongatedbimetallic element in thermal association with a resistance type ofheater.

.One well known bimetallic switching device of the prior art is of theambient compensated type and employs two generally fiat elongatedbimetallic elements one of which is encased in and thermally associatedwith a resistance heater of tubular configuration. In such a device,thermal lag between the heater and the bimetal can cause overheating ofthe bimetallic element whenever the heater is energized in excess of itsdesigned cycling time under abnormal operating conditions. This willproduce adverse efiects. For such a device, it has been found desirableto provide a simplified means for protecting the bimetallic element fromoverheating.

An important object of the present invention is to provide an improvedbimetallic switch which includes a simplified means for protecting abimetallic element thereof from overheating.

Another object of my invention is to provide an improved ambientcompensated bimetallic switch which includes a simplified means forprotecting a bimetallic element thereof from overheating under abnormaloperating conditions but does not affect operation thereof under normalconditions.

A further object of my invention is to provide an improved thermallyresponsive device which includes a protective switch involving a minimumnumber of parts.

A still further object of my invention is to provide a bimetallicelement and a tubular resistance heater cooperatively associatedtherewith in such a manner that the heater is rotated by curvature ofthe bimetallic element to provide thermal protection for the element.

In carrying out my invention, in one form thereof, I have provided athermally responsive switching unit comprising a supporting means and atleast one elongated bimetallic element mounted thereon. The bimetallicelement extends outwardly in cantilever fashion from the supportingmeans and carries a movable contact on the free end thereof forcooperative engagement with another contact. An elongated resistanceheater of tubular configuration is fitted loosely around the bimetallicelement and is in cooperative engagement with the element between thesupporting means and the movable contact. With such an arrangement, inaccordance with the present invention, a movable contact of a protectiveswitch is connected to and supported by a laterally extending firstterminal of the heater, located near one end of the heater. A biasingspring is connected between the free end of the bimetallic element andan adjacent second terminal of the heater located near its other end, toimpart a rotative biasing force to the heater which normally urges themovable contact of the protective switch into engagement with anassociated fixed contact of the protective switch. When the elongatedbimetallic element is heated to a predetermined critical temperature,curvature of the bimetallic element causes interference between it andthe tubular heater, and the biasing force applied to the heater by thespring is thereupon overcome to rotate the tubular heater about its axisand open the protective switch contacts. By means of an additional pairof switch contacts and a spring, a simplified and elfective mechanismhas 7 3,210,502 Patented Oct. 5, 1965 thus been provided for protectinga heater operated thermal switch from adverse effects due to abnormaloperating conditions. It, therefore, will be apparent that such anarrangement is readily manufacturable, low in cost, and adaptable tonumerous prior art thermally responsive devices.

Further aspects of my invention will become apparent hereinafter, andthe specification concludes with claims particularly pointing out anddistinctly claiming the subject matter which I regard as my invention.The invention, however, as to organization and method of operation,together with other objects and advantages thereof, may best beunderstood by reference to the following description, when taken inconjunction with the accompanying drawing, in which:

FIG. 1 is a partially broken away perspective view of a thermallyresponsive timing device embodying my invention;

FIG. 2 is a side elevational view of the device of FIG. 1, with theheater operated bimetallic element under normal ambient conditions;

FIG. 2a is a sectional view taken along the line 2a-2a of FIG. 2;

FIG. 2b is a right end view of the heater operated bimetallic assemblyof FIG. 2, with the movable contact screw removed;

FIG. 3 is a view similar to the heater operated bimetallic element andheater arrangement of FIG. 2, but showing the bimetallic element afterthe heater has been energized for an extended period of time;

FIG. 3a is a sectional view taken along the line 3a-3a of FIG. 3;

FIG. 3b is a right end view of the heater operated bimetallic assemblyof FIG. 3, with the movable contact screw removed;

FIG. 4 is a view similar to FIG. 3, but showing the bimetallic elementafter the heater has been energized for a prolonged period;

FIG. 4a is a sectional view taken along the line 4a4a of FIG. 4;

FIG. 4b is a right end view of the heater operated bimetallic assemblyof FIG. 4, with the movable contact screw removed; and

FIG. 5 is a circuit diagram showing schematically the employment of thethermally responsive timing device of FIG. 1.

Referring to the drawing, and initially to FIGS. 1 and 2 thereof, thereis illustrated a thermal timing device 1 which, briefly stated,comprises a supporting plate 3 of thin insulating material, a pair ofmatched upper and lower bimetallic elements 5 and 7 mounted in spacedparallel relationship on plate 3, a pair of mating contacts 9 and 11mounted respectively on the free ends of elements 5 and 7, and aresistance type heater 13 surrounding and in thermal association withthe upper bimetallic element 5.

For mounting the bimetallic elements 5 and 7 in insulated relationshipupon plate 3 and securing associated bimetal terminals 15 and 17respectively thereto, as further shown in FIGS. 1 and 2, a pair ofscrews 19 are provided. The screws 19 are suitably extended throughaligned apertures formed respectively in stacked upper clamping plate21, insulating spacer 23, the supported end 25 of bimetallic element 5,terminal 15, insulating spacer 27, a terminal 29, insulating spacer 31,terminal 17, the supported end 33 of bimetallic element 7, insulatingspacer 35, an end of supporting plate 3, the threaded lower clampingplate 37.

As further shown in FIG. 2, the bimetallic elements 5 and 7 are of fiatand elongated construction, and they are supported in cantilever fashionfrom their ends 25, 33. Elements 5, 7 each have their high expansionside facing upwardly and their low expansion side facing downward- 1y toprovide ambient compensation for the contacts 9, 11. Thus moreparticularly, the contacts 9, 11 are normally in an open relationship(FIG. 2) when both bimetallic elements are at the same temperature, andthe tip gap or spacing between these contacts when they are in thisrelationship will be maintained substantially constant (e.g., 0.005inch) over a wide range of ambient conditions (e.g., -30 F. to 120 F.).The contacts 9, 11 are arranged to close when the temperature of theheated bimetallic element 5 reaches a predetermined condition (e.g., F.)warmer than that of bimetallic element 7. It will thus be seen that theelectrically heated bimetallic element 5 serves as the main thermallyoperable means for actuating the contacts 9, 11, and element 7 serves asan ambient compensating means for the switch contacts 9, 11.

Tuming now to an important aspect of the present invention whichconcerns an improved means for preventing overheating of an electricallyheated bimetal under abnormal operating conditions without aifecting theeflicient operation or timing under normal conditions, attention isdirected to FIGS. 2, 2a and 2b. The resistance heater 13 is elongated,relatively fiat and of generally oblong cross section (FIG. 2a), havingan elongated tunnel 39 formed therethrough (as also shown in FIG. 4) ofsimilar configuration. Terminal tabs 41 and 43 of heater 13 extendlaterally outwardly from the longitudinal axis thereof, as best shown inFIG. 1, and are located respectively near opposite ends of heater 13.Each of the tabs 41, 43 is thus located on the same side of the heater(FIG. 1) and they are generally parallel to the top and bottom walls 45,47 of the heater (FIGS. 2 and 2a). Tab 43 is located near the free endof bimetallic element 5, and includes an aperture 49 formed therein(FIG. 1), the purpose of which shall become apparent hereinafter. Tab 41is located near the supported end 25 of element 5 and has a movablecontact supporting arm 44 secured thereto, such as by welding. Themovable arm 44 and its mode of operation forms an important aspect of myinvention, as shall be set forth in detail hereinafter.

The elongated bimetallic element 5 is extended through tunnel 39 of theheater 13, and fits loosely therein, as shown in FIG. 2a so that theheater 13 has freedom for limited rotation on element 5. Heater 13 thusloosely surrounds and is supported by element 5, being rotatable thereonbetween slotted free end 51 and the supported end 25 of element 5. Theloose relationship between heater 13 and element 5 prevents the heater13 from affecting the tip gap or spacing between contacts 9, 11 undernormal conditions. To enable the rotative move ment of heater 13 to beeffectively utilized for preventing overheating of 'bimetal 5, asfurther shown in FIGS. 1 and 2b, a piece of spring wire 53 is connectedbetween the slotted free end 51 of the bimetallic element 5 and theterminal tab 43 of heater 13, to normally rotatively bias the heater 13relative to its supporting element 5 into the position shown in FIG. 2a.

More particularly, one end 55 of the spring wire 53 is extended upwardlyfrom underneath the element 5 and threaded through the slotted end 51thereof (viewing FIG. 2b). The wire 53 is then bent over to the left ofthe underside of element end 51 (viewing FIG. 2b), and doubled backaround the left sideand top surface of end 51 (i.e., toward the rightside of end 51) to form a loop 57 for securing the wire 53 to element 5.The wire is then bent around the other side of the element 5 (i.e., theright side, viewing FIG. 2b) and back underneath toward the generaldirection of terminal tab 43. A looped over end 59 of the wire 53 isthen formed and engaged with aperture 49 of the terminal tab 43, asshown in FIGS. 1 and 2. The spring wire 53 is stressed by arranging itin such a manner as described, to apply a torsional moment upon theheater 13 at terminal tab 43. This torsional moment biases the heater ina counterclockwise direction of rotation (viewing FIG. 2a) and causesthe heater to normally assume a position relative to element 5 as shownin FIG. 2a. When the bimetallic element 5 is in this condition, it isrelatively flat and coplanar along its entire length and the uppersurface 5a of element 5 is spaced from the upper Wall or ceiling oftunnel 39 of the heater.

As previously mentioned, the terminal tab 41 of heater 13 has a movablecontact supporting arm 44 secured thereto (FIG. 1). The arm 44 isattached at one of its ends to an underside of tab 41, and it has acontact 61 formed on the bottom of its other end (FIG. 2). Arm 44extends in a direction generally parallel to the longitudinal axis ofheater 1,3, and toward the left of tab 41 (viewing FIG. 2) so that thecontact 61 overlies a mating contact 63 facing upwardly from a tab-liketerminal section 65 of terminal 29. Thus, as shown in FIGS. 1 and 2, thecontacts 61, 63 form a switch operable by rotative movement of heater13. This switch has been provided for effectively preventing overheatingof the electrically heated bimetallic element 5, as shall now bedescribed.

Turning now to a description of the operation of my improved thermallyresponsive device, attention is initially directed to FIGS. 2, 2a, 2band 5. As shown in FIG. 5, the thermal timing device may be connectedinto a circuit for eifectively controlling the timed energization of anelectric light L. For this purpose, an energizing circuit for the lamp Lis provided upon closure of timer contacts 9, 11, from line terminal L1through terminal 15, bimetallic contact carrying element 5, bimetalliccontact carrying element 7, terminal 17, and lamp L to line terminal L2.A control circuit for energizing the heater 13 of bimetallic element 5is also connected across the line terminals L1 and L2 and includesterminal 15, bimetallic contact carrying element 5, spring 53, heater13, protective contacts 61, 63, and a normally open pushbutton switch S.

When the thermal timing device 1 is subjected to normal ambientconditions, as shown in FIG. 2, bimetallic element 5 is substantiallyflat and generally parallel to the plane of plate 3. The maincontrolling contacts 9, 11 of the bimetallic elements 5 and 7 are thenin their normally open position and there is a relatively small gapwhich spaces these contacts apart. No current thus flows between theterminals 15 and 17 of the bimetallic elements 5 and 7, these terminalsbeing suitably connected in series with an electrically energizabledevice, such as the electric light L, which is to be controlled. Thetorsional moment of biasing force which is applied to the heater 13 byspring 53, causes the heater to assume the rotational position relativeto element 5, wherein it is shown in FIG. 2a, and the overload contacts61, 63 are spring biased into a closed position (FIG. 2). Under thiscondition, there is relatively little, if any, interference, such asbinding between the bimetallic element 5 and tunnel 39 of heater 13,since the upper and lower surfaces 5a and 5b of the element 5 are inloose engagement with or spaced from adjacent surfaces of the: tunnel.The spring biasing force applied to heater 13 by spring 53 and thecontact pressure applied thereby to con.

tacts 61, 63 has no appreciable effect upon the operative: movement ofthe free end of the bimetallic element 5 be-- cause the biasing force isa torsional force (and not a linear force), and also because the contactpressure for contacts 61, 63 is applied in vertical alignment with thesupported end 25 of element 5 (viewing FIGS. 2, 3 and 4). Thus moreparticularly, since the contact pressure for protective switch contacts61, 63 is exerted upon the fixed contact terminal 29 to the left of thecantilevered part of bimetallic element 5 and in general verticalalignment with supported end 25 of element 5 (FIG. 2), the bimetallicelement is allowed to operate with substantially the same thermalwarpage response under normal Operating conditions as if the spring 53and contacts 61, 63 were not being utilized.

In FIG. '2 near the free end of bimetallic element 5 there is shown areference dimension A which represents the travel of the free end ofelement 5 under normal operating conditions. Such a travel as this maybe alfected by depressing the actuator of pushbutton switch S andholding in this actuator for approximately 8 seconds. This causescurrent to flow through the heater circuit, and the free end ofbimetallic element 5 warps downwardly to close the contacts 9, 11 forenergizing lamp L. Under temperature conditions producing such a travelas this, no interference such as binding occurs between the bimetallicelement 5 and heater 13 (FIG. 2a), and the protective contacts 61, 63will remain in their closed position.

When the heater 13 is energized for an extended period of time (i.e., aperiod of time longer in duration than the desirable normal operatingrange for the bimetallic element 5), the temperature of bimetallicelement 5 in creases to beyond a predetermined limit, and the free endof the element 5 will move from its position in FIG. 2 to the positionshown in FIG. 3. In FIG. 3 reference dimension B has been shown toindicate a travel of the free end of element 5 from its normalhorizontal position, which is greater in magnitude than travel dimensionA of FIG. 2. As the element 5 is heated to the condition illustrated inFIG. 3, it warps by curving between its ends, and as a result,engagement in the form of binding occurs between the element 5 andheater 13 (see also FIGS. 3a and 3b).

Thus, more particularly, for example, the left side and edge of uppersurface 5a of element 5 (FIG. 3a) near the middle of the heater (FIG. 3)may engage the upper wall of tunnel 39 of heater 13 (FIG. 3a), and theright side and edge of lower surface 5b (FIG. 3a) of section In (nearthe free end 51 as shown in FIG. 3) of the element may engage the lowerwall of tunnel 39 at one of its ends. In addition, the right side andedge of lower surface 5b (FIG. 3a) of section It (near the supported endof the element) may also engage the lower wall of the tunnel at itsopposite end. Such engagement at this, which is caused by the thermalcurvature of element 5 coacting with heater 13, applies a generallyclockwise torsional moment to the heater 13 (viewing FIG. 3a) whichovercomes the spring biasing force and opens the protective contacts 61,63. As a result of rotary movement of the heater 13 with respect to itssupporting bimetallic element 5, the control circuit to the heater 13(which includes bimetal 5, spring 53, heater 13, contacts 61, 63 andswitch S) is thus interrupted, to prevent overheating of the bimetallicelement 5. The circuit to light L remains closed.

After the protective contacts 61, 63 of the overload switch have beenopened, continued heating of the bimetallic element 5 as a result of thethermal lag between it and the heater 13, may cause the protector switchcontacts 61, 63 to open further from their FIG. 3a position (where thereis a relatively small contact spacing) to an amount shown in FIG. 4.This is as a result of further thermal warpage of element 5 andincreased rotation of the heater 13 caused by the binding between thebimetallic element 5 and heater 13, as shown in FIGS. 4a and 4b. In FIG.4, the reference dimension C has been shown to indicate the travel ofthe free end of element 5 from its normal horizontal position (FIG. 2).

After the control circuit energizing heater 13 through bimetallicelement 5 has been deenergized by opening contacts 61, 63 of theprotective switch, if the switch S in series with contacts 61, 63 is inan open position, the bimetallic element 5 will then cool down andreturn to its relatively flat position, as shown in FIG. 2. The contacts9, 11 which are operated by the thermal timer 1 are thereupon reopenedto deenergize the circuit to the light L. As the bimetallic element 5returns from the position illustrated in FIG. 4 to the position of FIG.2, the binding force exerted upon the heater 13 by element 5 diminishesto a point where it allows the force of biasing spring 53 to return theheater to the rotational position wherein it is shown in FIG. 2a. Spring53 thus causes the heater 13 to rotate in a counterclockwise directionrelative to element 5 (viewing FIG. 2a) until protector contacts 61, 63close to their normal position. The control circuit to heater 13 maythus again be energized across the line by actuating switch S to itsclosed position. In the event that the normally open switch S whichcontrols energization of the heater 13 fails to reopen after apredetermined interval under normal conditions, upon reclosure ofcontacts 61, 63 the control circuit to heater 13 is again energizedacross the line.

If the protective contacts 61, 63 open when switch S is closed, it willbe further understood from viewing FIG. 5 that these contacts willthereupon cycle from one position to another to protect the bimetallicelement 5 from overheating.

By way of example, the thermally responsive device 1 illustrated anddescribed hereinbefore may be effectively utilized for closing a circuitto the light L within 2-4 seconds after heater 13 is energized, and tomaintain the light circuit for approximately 1 /2 minutes whenever theheater 13 is energized for approximately 8 seconds by the actuation ofswitch S. It will thus be seen by those skilled in the art that thedevice 1 can provide a relatively rapidly acting thermal responsetogether with a relatively long time delay.

It will now therefore be seen that I have provided a new and improvedthermally responsive device wherein a pair of protective contacts and aspring prevent overheating of an electrically heated bimetal. It willalso be realized that such an approach is simplified in construction andreadily lends itself to economy of manufacture. In accordance with myinvention, it will be further understood that a biasing spring has beenutilized in a thermally responsive device in such a manner that it notonly provides contact pressure, but also provides an electricalconnection between a resistance heater and a bimetallic elementthermally associated therewith.

While in accordance with the patent statutes, I have described what atpresent is considered to be the preferred embodiment of my invention, itwill be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from my invention,and I therefore aim in the following claims to cover all such equivalentvariations as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure Patent of the United States is:

1. A thermally responsive device comprising a supporting means, anelongated bimetallic element mounted on and extending from saidsupporting means for actuating a first switch, an electric heater coilhaving an elongated tunnel therethrough, said tunnel being of greatercross sectional dimension than said bimetallic element, a portion ofsaid bimetallic element extending from said supporting means, said coilsupported on said bimetallic element for limited movement thereon and inthermal association therewith, a heater switch having a movable contactand a mating contact, said movable contact being carried by said heaterfor movement therewith, said heater switch connected in circuit withsaid heater, biasing means urging said heater into a first positionabout said element, said element engaging with the walls of said tunneland effecting a movement of said heater against the bias of said biasingmeans and away from said first position when said bimetallic elementswarpage exceeds a predetermined amount, said heater abutting saidmovable switch contact against said mating contact of said heater switchwhen said heater is in its first position and separating said movablecontact from the mating contact when said heater is moved away from saidfirst position to protect said bimetallic element from damage.

by Letters 2. A thermally responsive device comprising a supportingmeans; an elongated bimetallic element mounted on said supporting meansand extending along its longitudinal axis in cantilever fashiontherefrom; an elongated heater supported on said bimetallic element andin thermal association therewith, said heater being supported on saidelement for limited rotational movement about said longitudinal axis ofsaid element; biasing means urging said heater to a first rotatedposition; said heater being rotated about said longitudinal axis of saidelement from said first position in response to a predetermined thermalwarpage of said element; and a switch connected to said heater andactuated by said heater as said heater rotates.

3. A thermally responsive device comprising a supporting means; anelongated bimetallic element mounted on and extending along itslongitudinal axis in cantilever fashion from said supporting means; anelongated heater mounted on and extending along said longitudinal axisof said bimetallic element, said heater being in thermal associationwith said element and being capable of rotating about said longitudinalaxis; a movable contact carried by said heater; and means engaging saidheater to normally bias said heater in one rotational direction aboutsaid longitudinal axis and thereby normally maintain said contact in oneposition; said elongated bimetallic element being thermally responsiveto a predetermined temperature to engage said heater and apply a forcethat rotates said heater about said longitudinal axis in opposition tosaid one direction and thereby move said contact to a second position.

4. A thermally responsive device comprising a supporting means, firstand second bimetallic elements mounted in cantilever fashion on saidsupporting means in spaced apart parallel relationship, said bimetallicelements having mating contacts of a first switch on the free endsthereof, said bimetallic elements being mounted on said support withtheir high expansion sides facing in the same direction to provideambient compensation for the first switch, an elongated heatersurrounding one of said bimetallic elements and being mounted on saidone element for limited movement thereabout, said heater being inloosely fitted thermal association, said heater moving about said oneelement in response to said one elements warpage, and a second switchconnected to said heater and actuated by said heater in response to themovement thereof for protecting said one bimetallic element from beingoverheated by said heater.

5. The device of claim 4 wherein the heater has an elongated tunnel ofoblong cross-section formed therein, said one bimetallic element havingan oblong cross section smaller than that of said tunnel and beingextended through said tunnel in such a manner that said heater isloosely supported upon said one element and arranged for limitedrotative movement with respect thereto.

6. The device of claim 4 wherein said second switch is in series circuitwith said heater.

7. The device of claim 4 wherein the second switch is located adjacentthe supporting means.

8. A thermally responsive device comprising a supporting means, firstand second bimetallic elements mounted in cantilever fashion on saidsupporting means and extending from said supporting means in spacedapart parallel relationship, said bimetallic elements having matingcontacts of a first switch on the free ends thereof, said bimetallicelements being mounted in said device with their high expansion sidesfacing in the same direction to provide ambient compensation for thefirst switch, an elongated heater surrounding one of said bimetallicelements and supported therearound, said heater having limited movementrelative to said one bimetallic element in response to a predeterminedthermal warpage of said element, and a second switch mounted in saiddevice adjacent said supporting means, said second switch being engagedwith said heater for actuation by said heater in response to themovement thereof for protecting said one bimetallic element from beingoverheated by said heater while not affecting the normal operation ofsaid first switch.

9. A thermally responsive device comprising a supporting means, firstand second bimetallic elements mounted on and extending in cantileverfashion from said supporting means, said elements being mounted inspaced apart parallel relationship and having contacts of a first switchon the free ends thereof, said bimetallic elements mounted on saidsupport with their low expansion sides facing in the same direction toprovide ambient compensation for the first switch, an elongated heatermounted on one of said bimetallic elements, said heater being in thermalassociation with said one element and having limited rotative movement,a second switch mounted in said device adjacent said supporting meansand actuated by said heater as said heater totates, and a spring locatednear the free end of said one bimetallic element and engaged betweensaid one element and said heater and normally biasing said heater in onedirection of rotation thereby to normally maintain said heater in oneposition, said one bimetallic element warping in response to apredetermined temperature to bind against said heater and rotate saidheater in opposition to the bias of said spring thereby to rotate saidheater in an opposite direction of rotation, said heater actuating saidsecond switch between open and closed positions as said heater rotatessaid second switch being in series circuit relation with said heater,whereby said second switch is operable by said heater to protect saidone bimetallic element from overheating without affecting the normaloperation of said first switch.

10. The device of claim 9 wherein the biasing spring is also utilizedfor connecting the heater into series circuit relationship with saidsecond switch.

11. A thermal timing system for an electrically energizable devicecomprising a circuit controlled by said device; a thermal timing switchin said circuit for controlling said circuit, said timing switch havingat least one bimetallic contact carrying element having a longitudinalaxis; a heater surrounding said bimetallic element and extending alongsaid longitudinal axis in thermal association therewith, said heaterbeing rotated about said longitudinal axis when said element impingesagainst said heater in response to a predetermined thermal warp-' age ofsaid element; an energizing circuit connected with said heater; and aprotective switch in said ener-' gizing circuit, said protective switchbeing actuated by said heater in response to a rotational movementthereof to energize said heater, said energizing circuit including saidbimetallic element, said heater, and said protective switch.

References Cited by the Examiner UNITED STATES PATENTS 1,402,417 1/22Hamilton 200113 2,192,631 3/40 Beam 200122 X. 2,371,018 3/45 AshWorth etal.. a 200122 2,589,614 3/52 Ireland 2l9511 X- 2,643,311 6/53 Giuffridaet a1. 200122 3,031,551 4/62 White et al ZOO-138.

BERNARD A. GILHEANY, Primary Examiner.

1. A THERMALLY RESPONSIVE DEVICE COMPRISING A SUPPORTING MEANS, ANELONGATED BIMETALLIC ELEMENT MOUNTED ON AND EXTENDING FROM SAIDSUPPORTING MEANS FOR ACTUATING A FIRST SWITCH, AND ELECTRIC HEATER COILHAVING AN ELONGATED TUNNEL THERETHROUGH, SAID TUNNEL BEING OF GREATERCROSS SECTIONAL DIMENSION THAN SAID BIMETALLIC ELEMENT, A PORTION OFSAID BIMETALLIC ELEMENT EXTENDING FROM SAID SUPPORTING MEANS, SAID COILSUPPORTED ON SAID BIMETALLIC ELEMENT FOR LIMITED MOVEMENT THEREON AND INTHERMAL ASSOCIATION THEREWITH, A HEATER SWITCH HAVING A MOVABLE CONTACTAND A MATING CONTACT, SAID MOVABLE CONTACT BEING CARRIED BY SAID HEATERFOR MOVEMENT THEREWITH, SAID HEATER SWITCH CONNECTED IN CIRCUIT WITHSAID HEATER, BIASING MEANS URGING SAID HEATER INTO A FIRST POSITIONABOUT SAID ELEMENT, SAID ELEMENT ENGAGING WITH THE WALLS OF SAID TUNNELAND EFFECTING A MOVEMENT OF SAID HEATER AGAINST THE BIAS OF SAID BIASINGMEANS AND AWAY FROM SAID FIRST POSITION WHEN SAID BIMETALLIC ELEMENT''SWARPAGE EXCEEDS A PREDETERMINED AMOUNT, SAID HEATER ABUTTING SAIDMOVABLE SWITCH CONTACT AGAINST SAID MATING CONTACT OF SAID HEATER SWITCHWHEN SAID HEATER IS IN ITS FIRST POSITION AND SEPARATING SAID MOVABLECONTACT FROM THE MATING CONTACT WHEN SAID HEATER IS MOVED AWAY FROM SAIDFIRST POSITION TO PROTECT SAID BIMETALLIC ELEMENT FROM DAMAGE.